Method of cold drawing sheet metal



Patented Oct. 14, 1952 METHOD OF GOLD DRAWING SHEET METAL Forrest Jerome Whitney, Jr., Wayne, Pa., assignor to Heintz Manufacturing Company, Philadelphia, Pa., a, corporation of Pennsylvania No Drawing. Application July 21, 1948, Serial No. 40,001

2 Claims. 1

This invention relates to a method of facilitating the drawing of metal sheets.

An object of the invention is to provide an improved method of cold working metal sheets which has the advantages of permitting faster operation of the metal working machinery, decreasing the number of imperfect articles made in the metal working process, and decreasing the number of delays occasioned by stoning the parts of the metal working machinery, such as dies and the like.

An example of the application of this invention is in the drawing of a metal tub by use of hard ened steel dies, the final product having a diameter of around 25 inches and a depth of about 24 inches, and formed from a circular fiat sheet of steeTTfor example of type AlSl Specification C1008) having a gauge of approximately .062.

Before putting the steel sheets through the drawing operations, a quantity of sheets to be coated are first washed in an alkaline bath to accomplish degreasing, after which they are rinsed in cold running water. The blanks are thereafter immersed in a bath having the following chemical composition:

Grams per liter Zinc 11.0 P205 9 to 9.5 N03 18 NazO 1.5 Ni 0.1 Cu 0.03 NaNOa 1 to 1 5 The above bath is preferably used at a pH of 2.8 to 2.9, and at a temperature of 20 to. 25 C'., with an immersion time of 3 to 5 minutes.

After treatment in the bath, the blanks are rinsed in cold running water and dried. The blanks after this treatment have a thin coating of zinc phosphate tightly adherent chemically to their surfaces.

After the phosphate coating operation, the coated blanks are put through three drawing operations, before each of which drawing operations the blanks are dipped or coated by swabbing, with a lubricant. Various types of lubricants are used, and among the most desirable are the following:

1. 1% sodium soap-99% water.

2. 2% sulphonated tallow98% water, with enough sodium hydroxide to produce a pH value of 8.

and the other of which is non-pigmented, the

two compositions following being used to adjust the lubricating conditions by addition to whichever of the three above-listed lubricants is being used.

Non-pigmented 24% animal fatty acid (lard, oil, or degras) 24% vegetable fatty acid (soy bean fatty acid) 6% solid alkali (NaOI-I) 10% chlorinated Wax Balance water.

Pigmented 24% animal fatty acid (lard, oil, or degras) 24% vegetable fatty acid (soy bean fatty acid) 6% solid alkali (NaOI-I) 10% chlorinated wax 20% pigment (talc, or inert clay) Balance water.

The two lubricants just described are used to adjust the lubricating conditions, the non-pigmerited lubricant being used for adjusting the conditions of the first draw, while the pigmented type disclosed can be used only for the second and third drawing operations, sinc it is too slippery for the first draw and would permit the blank to slide between the blank holders without getting a sufficient cup formed for the subsequent operation.

In one test operation of the type just described, 80 of the coated blanks were run through the dies, and only one of the 80 showed any evidences of pick-up by the dies, and friction was reduced as much as An astonishing and unexpected result followed the processing of the phosphate coated blanks, in that the processing of the 80 blanks was followed with drawing of an additional 70 uncoated blanks, and only one additional metal score from pick-up was observed in the 70 additional blanks, showing that the beneficial resultsvwere carried over (apparently by the dies). The results from the processing of the uncoated blanks are made all the more unusual when it is considered that in the ordinary stamping of the uncoated blanks using the same lubricants, but without previously processing a series of coated blanks, pickup occurred as frequently as every third or fourth draw, and caused bad scoring of the stampings. It was also necessary to stone the dies frequently under the previous practice because of the metal which the dies picked up from the blanks.

By using the new method and first running a series of coated blanks followed by a series of uncoated blanks, it is obvious that considerable savings in the use of the coating solution will be provided.

I claim:

1. In the cold deep drawing of steel sheets by means of dies, the steps of providing a thin chemically adherent coating of zinc phosphate on .a quantity of said sheets, applying to said quantity of sheets, a non-pigmented lubricant containing a high fatty acid radical which chemically reacts with said coating, cold deep drawing said quantity of sheets by the use of dies whereby there is transferred from said sheets to said dies as the deep drawing is effected material which includes at least some of the phosphate coating material and some of the product of said reaction, applying to a smaller quantity of uncoated steel sheets a non-pigmented lubricant of the same type as applied to the coated sheets, and cold deep drawing said second smaller quantity of sheets by the use of the same dies, the lubricants being selected from the group consisting of approximately one per cent sodium soap ninety-nine per cent water; approximately two per cent sulphonated tallow-ninety-eight per cent water, the pH of the lubricant being ap-, proximately 8; approximately one per cent chlorinated paraffin, forming an emulsion with approximately two per cent sodium soap, using approximately ninety-seven per cent water.

2. A process as defined in claim 1, the number of coated blanks being in the order of 80, and the number of uncoated blanks being in the order of 70.

FORREST JEROME WHITNEY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Mill Aug. 10, 1943 OTHER REFERENCES Number 

1. IN THE COLD DEEP DRAWING OF STEL SHEETS BY MEANS OF DIES, THE STEPS OF PROVIDING A THIN CHEMICALLY ADHERENT COATING OF ZINC PHOSPHATE ON A QUANTITY OF SAID SHEETS, APPLYING TO SAID QUANTITY OF SHEETS, A NON-PIGMENTED LUBRICANT CONTAINING A HIGH FATTY ACID RADICAL WHICH CHEMICALLY REACTS WITH SAID COATING, COLD DEEP DRAWING SAID QUANTITY OF SHEETS BY THE USE OF DIES WHEREBY THERE IS TRANSFERRED FROM SAID SHEETS TO SAID DIES AS THE DEEP DRAWING IS EFFECTED MATERIAL WHICH INCLUDES AT LEAST SOME OF THE PHOSPHATE COATING MATERIAL AND SOME OF THE PRODUCT OF SAID REACTION, APPLYING TO A SMALLER QUANTITY OF UNCOATED STEEL SHEETS A NON-PIGMENTED LUBRICANT OF THE SAME TYPE AS APPLIED TO THE COATED SHEETS, AND COLD DEEP DRAWING SAID SECOND SMALLER QUANTITY OF SHEETS BY THE USE OF THE SAME DIES, THE LUBRICANTS BEING SELECTED FROM THE GROUP CONSISTING OF APPROXIMATELY ONE PER CENT SODIUM SOAPNINETY-NINE PER CENT WATER; APPROXIMATELY TWO PER CENT SULPHONATED TALLOW-NINETY-EIGHT PER CENT WATER, THE PH OF THE LUBRICANT BEING APPROXIMATELY 8; APPROXIMATELY ONE PER CENT CHLORINATED PARAFFIN, FORMING AN EMULSION WITH APPROXIMATELY TWO PER CENT SODIUM SOAP USING APPROXIMATELY NINETY-SEVEN PER CENT WATER. 